Web supporting system



June 17, 1969 H. WEBER 3,450,322

WEB SUPPORTING SYSTEM Filed Jan. 19. 1967 Sheet of 2 June 17, 1969 A. WEBER 3,450,322

Filed Jan. 19, 1967 United States Patent 3,450,322 WEB SUPPORTING SYSTEM Harold Weber, Bloomfield, N.J., assignor to Celanese Corporation, New York, N.Y., a corporation of Delaware Filed Jan. 19, 1967, Ser. No. 610,398 Int. Cl. B65h 17/32, 25/04 U.S. Cl. 226-97 9 Claims ABSTRACT OF THE DISCLOSURE Background 0 the invention This invention relates to conveyor apparatus and more particularly to apparatus for supporting longitudinally advancing webs.

In conventional processes for casting sheets or webs of plastic material, such as cellulose acetate, the web is transferred from the casting wheel to a drier, where solvent or other liquid constituent are removed from the web. Usually, the soft web passes over a series of smooth rolls which support the soft Web while it is advancing continuously from the casting wheel to the drier. The vveb contacts the surface of the rolls which are driven at approximately the same surface speed as that of the web. Since the web is relatively soft, any pit marks or impressions on the surface of the rolls marks the surface of the web. Furthermore, there is a danger that the solvent in the web may build up on the surface of the rolls and adversley affect the transparency, strength, or other properties of the web.

Various systems have been proposed for overcoming the problems of utilizing conventional smooth rolls for supporting the Web. It has been proposed, for example, to provide a stationary roll with a plurality of orifices in the surface of the roll and to blow air outwardly through the orifices. The air issuing from the orifices serves as a cushion between the web and the roll surface. Supporting rolls of this type, however, are not entirely satisfactory. When the web is substantially more narrow than the length of the roll, the escape of air through the orifices that are beyond the marginal edges of the Web may be so great that the center of the web is unsupported and drags on the stationary surface of the roll. Another problem is that the holes or orifices form minute air jets which impinge on the surface of the web, and if the web is particularly soft, these air jets may cause streaking of the web.

Accordingly, it is an object of this invention to provide an improved system for supporting longitudinally advancing webs.

It is a further object of this invention to provide a conveyor system that supports a web uniformly across the width of the web.

Another object of this invention is to provide a conveyor system that does not produce streaking or other surface defects in the web.

Summary of the invention These objects are accomplished in accordance with a preferred embodiment of the invention by a stationary roll or shoe having a pair of slots extending transversely to the direction of movement of the web. The slots are extremely narrow in order to minimize variations in the velocity of air issuing from the slots due to the web overlying the intermediate portions of the slots but not the ends of the slots. The slots are formed by a key and keyway construction which permits the slots to be extremely narrow. In passing over the roll or shoe, the advancing web bends transversely, and the bight of the web is preferably offset from an axis midway between the slots in the direction of movement of the web.

Description of the drawings This preferred embodiment is illustrated in the accompanying drawings in which:

FIG. 1 is a front elevational view of the conveying system of this invention;

FIG. 2 is a side elevational view of the conveying system;

FIG. 3 is an enlarged front elevational view of one of the stationary conveying rolls;

FIG. 4 is a cross sectional view of the conveying roll along the line 4-4 in FIG. 3; and

FIG. 5 is a cross sectional view of the roll along the line 55 in FIG. 4.

Referring to FIGS. 1 and 2, the web supporting apparatus of this invention includes upright frame members 2 and 4. A plurality of non-rotating rolls 6 extend between the frame members 2 and 4 for supporting a longitudinally advancing web 8. The ends of the rolls 6 are supported on the frame members 2 and 4 by brackets 10'. The rolls 6 are preferably secured to the brackets 10 in such a way that the rotational position of the roll relative to the frame members may be adjusted according to the position of the web relative to the roll.

As shown in FIG. 3, each roll 6 includes a cylindrical shell 12 and end plates 14 and 16 which are rigidly secured to the shell 12 by a plurality of bolts 18. Preferably, the joints between the shell 12 and the end plates 14 and 16 are sealed to prevent the escape of air from the interior of the roll 6. The end plate 16 has a central opening 20 that has been drilled and tapped, and a conventional pipe plug 22 is secured in the tapped hole 20.

The end plate 14 has a central opening 24 that is internally threaded at 26 to receive a conventional pipe section. An orifice plate 28 is mounted in the opening 24 and is held in place by a snap ring 30 which cooperates with a shoulder in the opening 24. The orifice in the plate 28 limits the rate of flow of air into the interior of the roll 6.

The shell 12 has a longitudinal keyway 32, as shown in FIG. 4. A plurality of passages 34 extend through the shell 12 and communicate between the bottom of the keyway 32 and the interior of the shell 12. The passages 34 are spaced along the length of the keyway 32 to provide a uniform distribution of air lengthwise of the roll 6. A key 36 is mounted in the keyway and is held in place by screws 38 which extend through the shell 12.

The keyway 32 has a substantially uniform width that is slightly greater than the width of the key 36. The key 36 is centered in the keyway 32, so that slots 40 are provided between the sides of the keyway and the sides of the key 36. The slots 40 extend continuously from one end of the roll 6 to the other end.

Air under pressure is conducted to the interior of each roll 6 through separate conduits 42 that are connected with a common manifold 44 which receives air from a pump or other suitable source. Individual valves are provided in the conduits 42 for controlling the rate of flow to the rolls 6. As shown in FIG. 3, the conduits 42 are received in the threaded portion 26 of each end plate 14. The air introduced through the conduit 42 and through the orifice in the plate 28 flows outwardly through the passages 34 and through the slot 40 to the outer surface of the shell 12. The width of the slot 40 along each side of the key 36 is extremely narrow. For example, each slot may have a width of .004 and the width of the keyway may be about one-half inch. Since the slot is extremely narrow, a substantial pressure differential is maintained between the interior end of slots 40 and the exterior end of the slots at surface of the shell 12. Therefore, the loss of air at the ends of the roll 6, that are not covered by the web 8, does not have any substantial effect on the flow of air outwardly through the slots midway of the length of the roll.

Referring to FIG. 4, in orienting the roll 6 in the brackets 10, the central axis 46 of the key 36 and keyway 32 is preferably olfset from the axis about which the web 8 bends transversely in passing over the surface of the roll 6 as indicated schematically at 48. The central axis 46 is offset from the axis 48 in a direction opposite to the direction of motion of the web 8, as shown in FIG. 4, to compensate for the frictional drag of the boundary layer at the lower surface of the web 8. The air passing out of the slots 40 normally would flow outwardly as indicated by the arrows in FIG. 4, but due to the frictional drag of the lower surface of the web 8, the air passing out of the left hand slot in FIG. 4 is drawn between the web and the key 36, while the air passing out of the right hand slot 40 tends to be carried away from the key by the web 8. By offsetting the central axis of the key 36, the flow of air is approximately balanced so that a substantially uniform layer of cushioning air is provided between the web and the surface of the roll 6. The thickness of the air cushion, that is the spacing between the closest approach of the web 8 and the surface of the roll 12, is preferably about .010 inch.

In operation, the rolls 6 are arranged between the frame members 2 and 4 as shown in FIGS. 1 and 2, with the keyway axis 46 slightly offset from the bight axis 48 of the web, as shown in FIG. 4. The brackets 10 include means to permit the rotational position of the respective rolls to be adjusted, so that the axes 46 and 48 are in the relation shown in FIG. 4. Air under pressure is conducted from a source to the manifold 44 where it is distributed through the conduits 42 and through the orifice in the plate 28 to the interior of each roll 6. The air passes outwardly through the passages 34 and through the slots 40 to the outer surface of the shell 12 of each roll.

The width of the web has no significant effect on the rate of flow of air through the slots 40. Therefore, the web is supported on the air cushion uniformly across its width. Furthermore, the size of the orifice in the plate 28 limits the rate of flow of air into the slots 40 which contributes to a more uniform distribution of air.

Since the slots extend continuously across the rolls 6, there are no concentrations of air currents or air jets directed against the web, as there are in conventional rolls having a plurality of drill holes or other openings. The slots therefore tend to reduce the tendency for streaks or haze to develop on the surface of a soft web.

While this invention has been illustrated and described in one embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.

I claim:

1. Apparatus for supporting a web of continuously advancing flexible sheet material comprising an elongated web support member, said support member having an elongated keyway extending longitudinally thereon and an elongated key mounted in said keyway, the lateral edges of said key being spaced from the lateral edges of said keyway to form substantially parallel slots therebetween, and means for conducting fluid outwardly through said substantially parallel slots, whereby a web remains spaced from said bearing surface by the pressure on said web of fluid flowing out of said substantially parallel slots.

2. The apparatus according to claim 1 wherein said web support member is a roll of cylindrical configuration.

3. The apparatus according to claim 1 wherein said fluid conducting means includes a plenum chamber in said support member, said chamber being in communication with the entire length of said slots.

4. The apparatus according to claim 1 wherein said slots have a uniform width of about one-half of one hundreth of an inch.

5. The apparatus according to claim 1 wherein said support member is in the form of a hollow cylinder, the ends of said cylinder being sealed to form said plenum chamber, and fluid inlet means communicating with the interior of said cylinder.

6. The apparatus according to claim 5 including frame means, means mounting said support member in said frame means, means on said mounting means for adjusting the rotational position of said bearing surface relative to said frame.

7. The apparatus according to claim 5 wherein said keyway has a depth less than the thickness of the wall of said cylinder, said cylinder wall having a plurality of radial passages extending through said wall in alignment with said keyway, said passages being spaced apart along the length of said keyway, said keyway and key cooperating to form longitudinal passages therebetween, said longitudinal passages communicating between said radial passages and said slots.

8. The apparatus according to claim 5 wherein said inlet means includes an orifice plate for limiting the rate of flow into said cylinder.

9. In apparatus for supporting a continuously advancing web of flexible sheet material wherein the web passes over a plurality of support members mounted transversely on a frame, the support members changing the direction of travel of the web, the improvement comprising a plurality of support members having a pair of slots extending longitudinally of said members, said slots in each member being parallel, an individual plenum chamber communicating with the slots of each member, means for conducting fluid to each of said plenum chambers, means for adjusting the position of said slots relative to the bight imposed on said web at said support member, the central axis between said slots being offset from the center of said bight in the opposite direction from the web advancing direction.

References Cited UNITED STATES PATENTS 2,967,674 1/ 1961 Lawrence et al. 226-97 X 3,057,079 10/ 1962 Schmidt 226-97 X 3,109,572 11/1963 Herr 226-189 3,110,432 11/1963 Smith 226-189 X 3,189,240 6/1965 Emslie 226-97 X 3,227,017 1/1966 Bader 226-97 X 3,290,795 12/ 1966 Jarreby 226-97 X FOREIGN PATENTS 735,330 5/1966 Canada.

ALLEN N. KNOWLES, Primary Examiner.

US. Cl. X.R. 226-189, 199 

